<?php
   /*
   * File: CaptchaSecurityImages.php
   * Author: Simon Jarvis
   * Copyright: 2006 Simon Jarvis
   * Date: 03/08/06
   * Updated: 07/02/07
   * Requirements: PHP 4/5 with GD and FreeType libraries
   * Link: http://www.white-hat-web-design.co.uk/articles/php-captcha.php
   * 
   * This program is free software; you can redistribute it and/or 
   * modify it under the terms of the GNU General Public License 
   * as published by the Free Software Foundation; either version 2 
   * of the License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful, 
   * but WITHOUT ANY WARRANTY; without even the implied warranty of 
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
   * GNU General Public License for more details: 
   * http://www.gnu.org/licenses/gpl.html
   *
   */

   session_start();

   class CaptchaSecurityImages {
      var $font;

      function generateCode($characters) {
         /* list all possible characters, similar looking characters and
            vowels have been removed */
         $possible = '23456789bcdfghjkmnpqrstvwxyz';
         $code = '';
         $i = 0;
         while ($i < $characters) { 
            $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
            $i++;
         }
         return $code;
      }

      function __construct($width='120',$height='40',$characters='6') {
         if (!defined('ZOOWA')) {
            include_once('../../config.php');
         }
         $this->font = libspath.'monofont.ttf';
         $code = $this->generateCode($characters);

         /* font size will be 75% of the image height */
         $font_size = $height * 0.75;
         $image = imagecreate($width, $height) or
            die('Cannot initialize new GD image stream');

         /* set the colours */
         $background_color = imagecolorallocate($image, 255, 255, 255);
         $text_color = imagecolorallocate($image, 20, 40, 100);
         $noise_color = imagecolorallocate($image, 100, 120, 180);

         /* generate random dots in background */
         for( $i=0; $i<($width*$height)/3; $i++ ) {
            imagefilledellipse(
               $image,
               mt_rand(0,$width),
               mt_rand(0,$height),
               1,
               1,
               $noise_color);
         }

         /* generate random lines in background */
         for( $i=0; $i<($width*$height)/150; $i++ ) {
            imageline(
               $image,
               mt_rand(0,$width),
               mt_rand(0,$height),
               mt_rand(0,$width),
               mt_rand(0,$height),
               $noise_color);
         }

         /* create textbox and add text */
         $textbox = imagettfbbox($font_size, 0, $this->font, $code) or
            die('Error in imagettfbbox function');
         $x = ($width - $textbox[4])/2;
         $y = ($height - $textbox[5])/2;
         imagettftext(
            $image,
            $font_size,
            0,
            $x,
            $y,
            $text_color,
            $this->font,
            $code) or
            die('Error in imagettftext function');

         /* output captcha image to browser */
         header('Content-Type: image/jpeg');
         imagejpeg($image);
         imagedestroy($image);
         $_SESSION['captcha'] = $code;
      }
   }

   $width = '120';
   $height = '40';
   $characters = '6';
   $captcha = new CaptchaSecurityImages($width,$height,$characters);
?>